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PRESENTATION ONFARADAYS LAW
PRESENTED BY: RAZEENA AMEEN ROLL NO 25 BS(it)3rdPRESENTED TO: SIR TARIQ BHATTI
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Michael FaradayGreat experimental
physicist1791 – 1867Contributions to
early electricity include: – Invention of motor,
generator, and transformer
– Electromagnetic induction
– Laws of electrolysis
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InductionAn induced current is produced by
a changing magnetic fieldThere is an induced emf associated
with the induced currentA current can be produced without
a battery present in the circuitFaraday’s law of induction
describes the induced emf.
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EMF Produced by a Changing Magnetic Field, 1A loop of wire is
connected to a sensitive ammeter
When a magnet is moved toward the loop, the ammeter deflects– The direction was
chosen to be toward the right arbitrarily
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EMF Produced by a Changing Magnetic Field, 2When the magnet
is held stationary, there is no deflection of the ammeter
Therefore, there is no induced current– Even though the
magnet is in the loop
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EMF Produced by a Changing Magnetic Field, 3
The magnet is moved away from the loop
The ammeter deflects in the opposite direction
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EMF Produced by a Changing Magnetic Field, SummaryThe ammeter deflects when the magnet
is moving toward or away from the loopThe ammeter also deflects when the
loop is moved toward or away from the magnet
Therefore, the loop detects that the magnet is moving relative to it–We relate this detection to a change in
the magnetic field– This is the induced current that is
produced by an induced emf
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Faraday’s Experiment – Set Up
A primary coil is connected to a switch and a battery
The wire is wrapped around an iron ring
A secondary coil is also wrapped around the iron ring
There is no battery present in the secondary coil
The secondary coil is not directly connected to the primary coil
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Faraday’s Experiment – Findings At the instant the switch is closed, the
galvanometer (ammeter) needle deflects in one direction and then returns to zero
When the switch is opened, the galvanometer needle deflects in the opposite direction and then returns to zero
The galvanometer reads zero when there is a steady current or when there is no current in the primary circuit
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Faraday’s Experiment – Conclusions
An electric current can be induced in a circuit by a changing magnetic field– This would be the current in the secondary
circuit of this experimental set-upThe induced current exists only for a short
time while the magnetic field is changing This is generally expressed as: an induced
emf is produced in the secondary circuit by the changing magnetic field– The actual existence of the magnetic flux is
not sufficient to produce the induced emf, the flux must be changing
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Faraday’s Law – Statements Faraday’s law of induction states
that “the emf induced in a circuit is directly proportional to the time rate of change of the magnetic flux through the circuit”
Mathematically,
Bdεdt
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Faraday’s Law – Statements, contRemember B is the magnetic flux
through the circuit and is found by
If the circuit consists of N loops, all of the same area, and if B is the flux through one loop, an emf is induced in every loop and Faraday’s law becomes
B d B A
Bdε Ndt